Measurement The Parameter Of The Second Stage Cooling Of Atoms Of Strontium Optical Clock And Research The Miniaturization Of System

Preparing the cold Sr atom is a necessary step in developing Sr optical clock.First of all, we implemented the first-stage cooling to get around 108 atoms at 5m K. In this step, we utilized the dipole transition whose spontaneous emission rate is 2′108/s and linewidth is 32 MHz which corresponding to the 461 nm light. But the temperature of the atoms is too high to satisfy experiment requirement, so the second–stage cooling is necessary.In this step, we used the intercombination transition（5s²ï¼‰1S₀→（5s5p）³P₁ whose wavelength is 689 nm. Free-running laser linewidth is about to the MHz level, does not meet the second-stage cooling of the light source. Experiments pressured the laser linewidth by PDH technology. The cooling light is generated by 689 nm narrow linewidth laser. Through beat frequency experiment, we measured the laser linewidth is 300 Hz which is much less than the natural linewidth of intercombination transition7.6k Hz, so the cooling is effective. Then we measured the temperature of atoms through TOF（time of flight）, the concrete proposal is managing the interaction time of atoms and light by virtue of timing sequence, using the EMCCD recording the picture of atoms before and after expansion. Through analyzing the picture, we knew the atomsï¿  temperature is 4.39mK, and the number of atoms is 1.2′107. The temperature and number offer the important reference to the SNR（ Signal to Noise Ratio） for optical clock transition signal, and they’re also the premise of high precision time and frequency standard.Frequency locking system and physical system are the important parts of Sr optical clock. In this paper, we realized the miniaturization of the two systems. We also detected the fluorescence spectrum of 689 nm intercombination transition（the linewidth of intercombination transition is 26MHz） and measured the fluorescence intensity at different laser intensity or scanning frequency and tried to explain it. The flux of atomic beam has also been measured by LIF（Laser Induce Fluorescence）. The flux of atomic beam is proportional to the fluorescence intensity detected, so we used461 nm dipole transition and 689 nm intercombination transition measuring the flux of hot atomic beam. The physical systems volume of Strontium optical clock not only has been reduced for small the system, but also the Zeeman slower has been improved.The required magnetic is generated by the coil, instead of permanent magnetsgenerate the required magnetic field. It has many advantages such as small size, light weight, high current and water cooling is not required to meet the needs of space clock.